Systems and methods for dynamic control of filtration efficiency and fuel economy

ABSTRACT

An aftertreatment system comprises a SCR system, a first filter, and a second filter disposed downstream of the first filter and a bypass conduit providing a flow path bypassing the second filter. A valve is operatively coupled to the bypass conduit and is moveable between a closed position in which the exhaust gas flows through the second filter, and an open position in which at least a portion of the exhaust gas flows through the bypass conduit. A controller is operatively coupled to the valve configured to adjust the valve based on a first filtration efficiency of the first filter to cause the exhaust gas expelled into the environment from the aftertreatment to have a particulate matter count meeting particulate matter emission standards.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Phase Application ofPCT/US2018/053400, filed Sep. 28, 2018, the contents of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to aftertreatment systems foruse with internal combustion (IC) engines.

BACKGROUND

Exhaust aftertreatment systems are used to receive and treat exhaust gasgenerated by IC engines. Generally exhaust gas aftertreatment systemscomprise any of several different components to reduce the levels ofharmful exhaust emissions present in exhaust gas. For example, certainexhaust gas aftertreatment systems for diesel-powered IC enginescomprise a selective catalytic reduction (SCR) system, including acatalyst formulated to convert NOx (NO and NO₂ in some fraction) intoharmless nitrogen gas (N₂) and water vapor (H₂O) in the presence ofammonia (NH₃). Aftertreatment systems may also include a filter such asa partial flow filter, configured to remove particulate matter (PM), forexample, soot, dust, inorganic particles, etc. from the exhaust gas.Increasingly stringent PM emission standards require the filter toremove PM with high filtration efficiency. Filters having highfiltration efficiency however, exert a high backpressure on exhaust gasflowing through the aftertreatment system which may reduce fuel economyof the engine.

SUMMARY

Embodiments described herein relate generally to systems and methods forcontrolling operation of an aftertreatment system for high filtrationefficiency or high fuel economy based on an operating condition of anengine producing the exhaust gas. In particular, embodiments describedherein relate to aftertreatment system that include a first filter, asecond filter having a smaller pore size than the first filterpositioned downstream of the first filter for providing high filtrationefficiency, and a bypass conduit for selectively bypassing flow of theexhaust gas around the second filter when high fuel economy is desiredwhile meeting PM emission standards.

In some embodiments, an aftertreatment system configured to reduceconstituents of an exhaust gas produced by an engine comprises a firstfilter and a second filter disposed downstream of the first filter. Abypass conduit fluidly couples an exhaust gas flow path downstream ofthe first filter and upstream of the second filter to an exhaust gasflow path downstream of the second filter. A valve is operativelycoupled to the bypass conduit, the valve moveable between a closedposition in which the exhaust gas flows through the second filter, andan open position in which at least a portion of the exhaust gas flowsthrough the bypass conduit so as to bypass the second filter. Acontroller is operatively coupled to the valve and is configured todetermine whether a first filtration efficiency of the first filter isgreater than a first filtration efficiency threshold or less than orequal to the first filtration efficiency threshold. The controller isconfigured to control the valve such that the valve is more closed whenthe first filtration efficiency is less than or equal to the firstfiltration efficiency threshold than when the first filtrationefficiency is greater the first filtration efficiency threshold, suchthat a larger portion of the exhaust gas flows through the second filterwhen the first filtration efficiency is less than the first filtrationefficiency threshold, the controlling of the valve causing the exhaustgas expelled into the environment from the aftertreatment system to havea PM count which is lower than a predetermined threshold.

In some embodiments, an aftertreatment system configured to reduceconstituents of an exhaust gas produced by an engine comprises, a firstfilter, and a second filter disposed downstream of the first filter. Abypass conduit fluidly couples an exhaust gas flow path downstream ofthe first filter and upstream of the second filter to an exhaust gasflow path downstream of the second filter. A valve is operativelycoupled to the bypass conduit. The valve is moveable between a closedposition in which the exhaust gas flows through the second filter, andan open position in which at least a portion of the exhaust gas flowsthrough the bypass conduit so as to bypass the second filter. Acontroller is operatively coupled to the valve. The controller isconfigured to determine whether the engine is operating in a highparticulate matter operating condition or a low particulate matteroperating condition. The controller is configured to control the valvesuch that the valve is more closed during the high particulate matteroperating condition of the engine than during the low particulate matteroperating condition of the engine, such that a larger portion of theexhaust gas flows through the second filter during the high particulatematter operating condition of the engine than during the low particulatematter operating condition of the engine, the controlling of the valvecausing the exhaust gas expelled into the environment from theaftertreatment system to have a PM count which is lower than apredetermined threshold.

In some embodiments, an aftertreatment system for reducing constituentsof an exhaust gas produced by an engine comprises a first filter and asecond filter positioned downstream of the first filter. A controller isoperably coupled to the first and second filters and is configured todetermine a first filtration efficiency of the first filter duringoperation of the aftertreatment system. In response to the firstfiltration efficiency being equal to or greater than a first filtrationefficiency threshold, the controller is configured to generate a faultcode instructing a user to remove the second filter from theaftertreatment system.

In some embodiments, a valve comprises a plurality of rings comprising afirst ring defining a plurality of first openings, and a second ringdefining a plurality of second openings. The second ring abuts the firstring. The valve is moveable between a closed position and an openposition. In the closed positioned, the plurality of first openings aremisaligned with the plurality of second openings to prevent a fluid fromflowing through the plurality of first and second openings. In the openposition, the second ring is rotated relative to the first ring suchthat the plurality of first openings are aligned with the plurality ofsecond openings allowing the fluid to flow therethrough.

In some embodiments, an aftertreatment system configured to reduceconstituents of an exhaust gas produced by an engine comprises a firstfilter and a second filter disposed downstream of the first filter. Abypass conduit fluidly couples at least one of an exhaust gas flow pathupstream of the first filter to an exhaust gas flow path between thefirst filter and the second filter or an exhaust gas flow path betweenthe first filter and the second filter to an exhaust gas flow pathdownstream of the second filter. A valve is operatively coupled to thebypass conduit, the valve moveable between a closed position in whichthe exhaust gas flows through the second filter, and an open position inwhich at least a portion of the exhaust gas flows through the bypassconduit so as to bypass the second filter. A controller is operativelycoupled to the valve. The controller is configured to determine whetherthe engine is operating in a high PM operating condition or a low PMoperating condition. The controller is configured to control the valvesuch that the valve is more closed during the high PM operatingcondition of the engine than during the low PM operating condition ofthe engine, such that a larger portion of the exhaust gas flows throughthe second filter during the high PM operating condition of the enginethan during the low PM operating condition of the engine, thecontrolling of the valve causing the exhaust gas expelled into theenvironment from the aftertreatment system to have a PM count which islower than a predetermined threshold.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the subject matter disclosed herein. In particular, all combinationsof claimed subject matter appearing at the end of this disclosure arecontemplated as being part of the subject matter disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claimstaken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are therefore not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 is a schematic illustration of an aftertreatment system,according to an embodiment.

FIG. 2 is a schematic flow diagram of an example method to controlfiltration efficiency of an aftertreatment system, according to anembodiment.

FIG. 3A is a schematic block diagram of an aftertreatment system,according to another embodiment.

FIG. 3B is a schematic block diagram of an aftertreatment system,according to another embodiment.

FIG. 4 is a schematic block diagram of an embodiment of a controlcircuitry that may be included in the aftertreatment system of FIG. 3Aor 3B.

FIG. 5 is a plot of a filter flow restriction vs filtration efficiencyfor an example filter.

FIG. 6 is a schematic illustration of an aftertreatment system,according to yet another embodiment.

FIG. 7A is a side perspective view of a portion of an aftertreatmentsystem showing a first filter, a second filter and a bypass conduit,according to an embodiment; FIG. 7B is a side perspective view of avalve disposed in the bypass conduit of the aftertreatment system ofFIG. 7A.

FIG. 8A is a side view of the portion of the aftertreatment system ofFIG. 7A with the valve being in a closed position, and FIG. 8B shows thevalve in an open position.

FIG. 9 is a schematic illustration of an aftertreatment system,according to still another embodiment.

FIG. 10 is a plot of overall filtration efficiency of an aftertreatmentsystem including a first filter and a second filter positioneddownstream of the first filter.

FIGS. 11A-11B are schematic flow diagrams of a method for dynamicallycontrolling filtration efficiency of an aftertreatment system, and fueleconomy of an engine fluidly coupled to an aftertreatment system,according to an embodiment.

FIG. 12 is a schematic block diagram of a computing device which may beused as the controller shown in FIG. 3A-3B, 4, 6 or 9, according to anembodiment.

Reference is made to the accompanying drawings throughout the followingdetailed description. In the drawings, similar symbols typicallyidentify similar components unless context dictates otherwise. Theillustrative implementations described in the detailed description,drawings, and claims are not meant to be limiting. Other implementationsmay be utilized, and other changes may be made, without departing fromthe spirit or scope of the subject matter presented here. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the figures, can bearranged, substituted, combined, and designed in a wide variety ofdifferent configurations, all of which are explicitly contemplated andmade part of this disclosure.

DETAILED DESCRIPTION

Embodiments described herein relate generally to systems and methods forcontrolling operation of an aftertreatment system for high filtrationefficiency or high fuel economy based on an operating condition of anengine producing the exhaust gas. In particular, embodiments describedherein relate to aftertreatment systems that include a first filter, asecond filter having a smaller pore size than the first filter andpositioned downstream of the first filter for providing high filtrationefficiency, and a bypass conduit for selectively bypassing flow of theexhaust gas around the second filter when high fuel economy is desiredwhile meeting PM emission standards.

Increasingly stringent PM emission standards on exhaust gas emitted fromaftertreatment systems require that filters included in aftertreatmentsystems remove PM with high filtration efficiency. For example, China isimplementing very strict regulations on PM emission from aftertreatmentsystems. Conventional aftertreatment systems only allow a shortpreconditioning time which creates challenges in the ash limited filterperformance. Filters included in conventional aftertreatment systems mayhave open pores which allow a large amount of PM (e.g., soot or ash) toflow therethrough during the preconditioning phase, for example, whenthe aftertreatment system is operated for the first time or afterregeneration of the filter when there is no PM, or negligible amount ofPM trapped in the filter. This allows a large amount of PM to flowthrough the filter during the preconditioning phase. While the PMaccumulation in the filter over time reduces the porosity of the filterand eventually increases the filtration efficiency of the filter to adesirable level, the passage of the higher amount of PM through thefilter during the preconditioning phase is undesirable. Filters havinghigh filtration efficiency can address the PM issue. However, suchfilters exert a high backpressure on the exhaust gas flowing through theaftertreatment system which reduces fuel economy of the engine.Moreover, conventional aftertreatment systems typically include thefilter located upstream of a location of an SCR system. This allows PMgenerated from the decomposition of reductant into the SCR system or topass out of the aftertreatment system unfiltered, increasing the PMcount. In some arrangements, reductant insertion can increase PM countdownstream of the filter by 400%-600% due to reductant insertion andreaction with the exhaust gas in the SCR system.

Various embodiments of the systems and methods described herein providebenefits including, for example: (1) providing a high filtrationefficiency during and after the preconditioning phase or during high PMoperating condition of an engine by disposing a second smaller pore sizefilter downstream or upstream of a first larger pore size filter; (2)reducing PM count during reductant insertion in the exhaust gas bydisposing the second filter downstream of an SCR system of theaftertreatment system; (3) providing high filtration efficiency duringhigh PM operating conditions and providing high fuel economy during lowPM operating conditions while meeting emission standards by selectivelybypassing at least a portion of the exhaust gas around the second filter(4) allowing installation in existing aftertreatment systems withminimum modifications; and/or (5) reducing durability concerns byallowing selective removal of the second filter from the aftertreatmentsystem.

FIG. 1 is a schematic illustration of an aftertreatment system 100,according to an embodiment. The aftertreatment system 100 is configuredto receive an exhaust gas from an engine (e.g., a diesel engine, agasoline engine, a natural gas engine, a dual fuel engine, a biodieselengine, an E-85 engine, or any other suitable engine) and reduceconstituents of the exhaust gas such as, for example, NOx gases, CO,hydrocarbons, etc. The aftertreatment system 100 may comprise areductant storage tank 110, a reductant insertion assembly 120, ahousing 101, a first filter 140, a second filter 142 and a SCR system150.

The housing 101 defines an internal volume within which the componentsof the aftertreatment system 100, i.e., the first filter 140, the secondfilter 142 and the SCR system 150 are positioned. The housing 101 may beformed from a rigid, heat-resistant and corrosion-resistant material,for example stainless steel, iron, aluminum, metals, ceramics, or anyother suitable material. The housing 101 may have any suitablecross-section, for example circular, square, rectangular, oval,elliptical, polygonal, or any other suitable shape.

An inlet conduit 102 is fluidly coupled to an inlet of the housing 101and structured to receive exhaust gas from the engine and communicatethe exhaust gas to an internal volume defined by the housing 101.Furthermore, an outlet conduit 104 may be coupled to an outlet of thehousing 101 and structured to expel treated exhaust gas into theenvironment (e.g., treated to remove PM such as soot and ash by thefirst and/or second filters 140 and 142 and/or reduce constituents ofthe exhaust gas such as NOx gases included in the exhaust gas).

A first sensor 103 may be positioned in the inlet conduit 102. The firstsensor 103 may comprise a NOx sensor configured to measure an amount ofNOx gases included in the exhaust gas flowing into the aftertreatmentsystem 100 and may include a physical NOx sensor or a virtual NOxsensor. In other embodiments, the first sensor 103 may comprise anexhaust gas flow rate sensor. In various embodiments, a temperaturesensor, a pressure sensor, an oxygen sensor or any other sensor may alsobe positioned in the inlet conduit 102 so as to determine one or moreoperational parameters of the exhaust gas flowing through the housing101 of the aftertreatment system 100.

A second sensor 105 may be positioned in the outlet conduit 104. Thesecond sensor 105 may comprise a second NOx sensor configured todetermine an amount of NOx gases expelled into the environment afterpassing through the SCR system 150. In other embodiments, the secondsensor 105 may comprise a PM sensor configured to determine an amount ofPM (e.g., soot or ash included in the exhaust gas exiting the filter140). In still other embodiments, the second sensor 105 may comprise anammonia sensor configured to measure an amount of ammonia in the exhaustgas flowing out of the SCR system 150, i.e., determine the ammonia slip.This may be used as a measure of determining a catalytic efficiency ofthe SCR system 150, adjust an amount of reductant to be inserted intothe SCR system 150, and/or adjust a temperature of the SCR system 150 soas to allow the SCR system 150 to effectively use the ammonia forcatalytic decomposition of the NOx gases included in the exhaust gasflowing therethrough. In some embodiments, an ammonia oxidation (AMOx)catalyst may be positioned downstream of the SCR system 150, forexample, in the outlet conduit 104 so as to decompose any unreactedammonia in the exhaust gas downstream of the SCR system 150.

In some embodiments, the aftertreatment system 100 may also include anoxidation catalyst 130 (e.g., a diesel oxidation catalyst) disposedupstream of the first filter 140, for example, in the housing 101. Theoxidation catalyst 130 may be configured to oxidize unburnt hydrocarbonsand/or carbon monoxide included in the exhaust gas to CO₂.

The SCR system 150 includes an SCR catalyst formulated to decomposeconstituents of an exhaust gas flowing therethrough. In someembodiments, the SCR system 150 may comprise a selective catalyticreduction filter (SCRF), or any other aftertreatment componentconfigured to decompose constituents of the exhaust gas (e.g., NOx gasessuch as such nitrous oxide, nitric oxide, nitrogen dioxide, etc.),flowing through the housing 101 in the presence of a reductant, asdescribed herein.

Any suitable SCR catalyst may be used such as, for example, rhodium,cerium, iron, manganese, copper, vanadium based catalyst, any othersuitable catalyst, or a combination thereof. The SCR catalyst may bedisposed on a suitable substrate such as, for example, a ceramic (e.g.,cordierite) or metallic (e.g., kanthal) monolith core which can, forexample, define a honeycomb structure. A washcoat can also be used as acarrier material for the SCR catalyst. Such washcoat materials maycomprise, for example, aluminum oxide, titanium dioxide, silicondioxide, any other suitable washcoat material, or a combination thereof.The exhaust gas (e.g., diesel exhaust gas) can flow over and/or aboutthe SCR catalyst such that any NOx gases included in the exhaust gas arefurther reduced to yield an exhaust gas which is substantially free ofNOx gases.

In various embodiments, the aftertreatment system 100 may also includeother aftertreatment components such as, for example, ammonia oxidationcatalysts, mixers, baffle plates, or any other suitable aftertreatmentcomponent.

A reductant port (not shown) may be positioned on a sidewall of thehousing 101 and structured to allow insertion of a reductanttherethrough into the internal volume defined by the housing 101. Thereductant port may be positioned upstream of the SCR system 150 (e.g.,to allow reductant to be inserted into the exhaust gas upstream of theSCR system 150) or over the SCR system 150 (e.g., to allow reductant tobe inserted directly on the SCR system 150). In other embodiments inwhich the reductant is inserted upstream of the SCR system 150, mixers,baffles, vanes or other structures may be positioned upstream of the SCRsystem 150 so as to facilitate mixing of the reductant with the exhaustgas.

The reductant storage tank 110 is structured to store a reductant. Thereductant is formulated to facilitate decomposition of the constituentsof the exhaust gas (e.g., NOx gases included in the exhaust gas). Anysuitable reductant can be used. In some embodiments, the exhaust gascomprises a diesel exhaust gas and the reductant comprises a dieselexhaust fluid. For example, the diesel exhaust fluid may comprise urea,an aqueous solution of urea, or any other fluid that comprises ammonia,by-products, or any other diesel exhaust fluid as is known in the arts(e.g., the diesel exhaust fluid marketed under the name ADBLUE®). Forexample, the reductant may comprise an aqueous urea solution having aparticular ratio of urea to water. In particular embodiments, thereductant can comprise an aqueous urea solution including 32.5% byvolume of urea and 67.5% by volume of deionized water, including 40% byvolume of urea and 60% by volume of deionized water, or any othersuitable ratio of urea to deionized water.

A reductant insertion assembly 120 is fluidly coupled to the reductantstorage tank 110. The reductant insertion assembly 120 is configured toselectively insert the reductant into the SCR system 150 or upstreamthereof (e.g., into the inlet conduit 102) or a mixer (not shown)positioned upstream of the SCR system 150. The reductant insertionassembly 120 may comprise various structures to facilitate receipt ofthe reductant from the reductant storage tank 110 and delivery to theSCR system 150.

In various embodiments, the reductant insertion assembly 120 may alsoinclude one or more pumps (e.g., a diaphragm pump, a positivedisplacement pump, a centrifugal pump, a vacuum pump, etc.) fordelivering the reductant to SCR system 150 at an operating pressureand/or flow rate. The reductant insertion assembly 120 may also includefilters and/or screens (e.g., to prevent solid particles of thereductant or contaminants from flowing into the one or more pumps)and/or valves (e.g., check valves) to receive reductant from thereductant storage tank 110.

Screens, check valves, pulsation dampers, or other structures may alsobe positioned downstream of the one or more pumps of the reductantinsertion assembly 120 and configured to remove contaminants and/orfacilitate delivery of the reductant to the SCR system 150. In variousembodiments, the reductant insertion assembly 120 may also comprise abypass line structured to provide a return path of the reductant fromthe one or more pumps to the reductant storage tank 110. A valve (e.g.,an orifice valve) may be provided in the bypass line. In variousembodiments, the reductant insertion assembly 120 may also comprise ablending chamber structured to receive pressurized reductant from ametering valve at a controllable rate. The blending chamber may also bestructured to receive air (e.g., compressed air or portion of theexhaust gas), or any other inert gas (e.g., nitrogen), for example, froman air supply unit so as to deliver a combined flow of the air and thereductant to the SCR system 150 through the reductant port.

The aftertreatment system 100 may also comprise a reductant injectorfluidly coupled to the reductant insertion assembly 120 and configuredto insert the reductant (e.g., a combined flow of reductant andcompressed air) into the SCR system 150. In various embodiments, thereductant injector may comprise a nozzle having predetermined diameter.In various embodiments, the reductant injector may be positioned in thereductant port and structured to deliver a stream or a jet of thereductant into the internal volume of the housing 101 so as to deliverthe reductant to the SCR system 150.

In various embodiments, the reductant insertion assembly 120 may alsocomprise a dosing valve, for example positioned within a reductantdelivery line for delivering the reductant from the reductant insertionassembly 120 to the SCR system 150. The dosing valve can comprise anysuitable valve, for example a butterfly valve, a gate valve, a checkvalve (e.g., a tilting disc check valve, a swing check valve, an axialcheck valve, etc.), a ball valve, a spring loaded valve, an air assistedinjector, a solenoid valve, or any other suitable valve. The dosingvalve may be selectively opened to insert a predetermined quantity ofthe reductant for a predetermined time into the SCR system 150 orupstream therefrom.

The first filter 140 is configured to remove PM (e.g., soot, debris,inorganic particles, etc.) from the exhaust gas. In various embodiments,the first filter 140 may include a ceramic filter. In particularembodiments, the first filter 140 may include a partial flow filter(e.g., a ceramic partial filter). In other embodiments, the first filter140 may include a metallic partial flow filter. In still otherembodiments, the first filter 140 may include a cordierite filter whichcan, for example, be an asymmetric filter. In yet other embodiments, thefirst filter 140 may be catalyzed.

The second filter 142 is disposed downstream of the first filter 140.While shown as being disposed upstream of the SCR system 150, in otherembodiments, the second filter 142 may be disposed downstream of the SCRsystem 150. The second filter 142 may include a ceramic filter, apartial flow filter, a cordierite filter or any other filter asdescribed with respect to the first filter 140. In some embodiments, thesecond filter 142 may include an uncoated filter.

In various embodiments, the first filter 140 may have a first pore sizewhich is larger than a second pore size of the second filter 142 suchthat the second filter 142 has a higher filtration efficiency than afirst filtration efficiency of the first filter 140. For example,certain emissions standards (e.g., in Europe or China) may place veryhigh restrictions on PM emission from aftertreatment systems. During apreconditioning stage (e.g., when the aftertreatment system 100 is newor after regeneration of the first filter 140) the first filter 140 mayhave a porosity which allows a larger amount of PM to pass therethroughthen is allowable by emission standards. Positioning the second filter142 having a small pore size and thereby, a higher filtration efficiencythan the first filtration efficiency of the first filter 140 downstreamof the first filter 140, allows filtering of a higher amount of PM fromthe exhaust gas than would be possible by the first filter 140. Forexample, the first filter 140 may have a first filtration efficiency of70%, and the second filter may 142 may have a second filtrationefficiency of 90% such that the aftertreatment system 100 has an overallfiltration efficiency of 1−(1−70%)×(1−90%)=97%, higher than each of thefilters 140 and 142 alone, thereby effectively meeting PM emissionstandards.

Over time as the exhaust gas continues to flow through theaftertreatment system 100, the first filter 140 may become increasinglyclogged with PM which causes a decrease in its porosity and increase inits filtration efficiency. Over time, the first filtration efficiency ofthe first filter 140 reaches a first efficiency threshold at which thefirst filter 140 is able to meet PM emission standards. The firstfiltration efficiency may be based on a pressure drop across the firstfilter 140 (e.g., measured using a differential pressure sensor) and anexhaust gas flow rate of the exhaust gas, for example, a ratio of thepressure drop to the exhaust gas flow rate.

While the first filter 140 becomes increasingly clogged with PMresulting in an increase in its filtration efficiency, the second filter142 also becomes increasingly clogged. This causes an increase in thebackpressure on the exhaust gas causing a decrease in fuel economy ofthe engine. The second filter 142 may be removably coupled to theaftertreatment system 100, such that in response to first filtrationefficiency first filter 140 reaching the first efficiency threshold, thesecond filter 142 may be removed from the aftertreatment system 100, forexample, during a scheduled maintenance of the aftertreatment system100, so as to decrease the backpressure. In some embodiments, the secondfilter 142 may be removed if a second pressure drop across the secondfilter 142 is greater than a predetermined pressure drop threshold whichmay correspond to a high backpressure.

In some embodiments, the aftertreatment system 100 may also comprise acontroller 170 communicatively coupled to the first filter 140 and/orthe second filter 142. In various embodiments, the controller 170 may beincluded in a control circuitry, for example, the control circuitry 371described in further detail herein. The controller 170 is configured todetermine the first filtration efficiency of the first filter 140 duringoperation of the aftertreatment system 100. For example, the firstfilter pressure sensor 138 (e.g., a differential pressure sensor or adelta pressure sensor) may be operatively coupled to the first filter140 and configured to determine a pressure drop across the first filter140. The controller 170 may be configured to interpret a pressure signalfrom the first filter pressure sensor 138 to determine a first pressuredrop across the first filter 140. The controller 170 may also beconfigured to determine a flow rate of the exhaust gas (e.g., from asignal received from an exhaust flow sensor or based on operatingcondition of the engine). The controller 170 may determine the firstfiltration efficiency based on the first pressure drop and the flow rateof the exhaust gas (e.g., a ratio of the first pressure drop to the flowrate).

In response to the pressure drop being greater than a predeterminedpressure drop threshold, the controller 170 generates a fault codeinstructing a user to remove the second filter 142 from theaftertreatment system 100. The fault code may be stored in a memory of acentral controller of a vehicle or any other assembly including theaftertreatment system 100, which may be retrieved during a maintenanceinterval of the vehicle. In other embodiments, the controller 170 mayalso activate an indicator lamp (e.g., an indicator on a dash display),thereby informing the user that the second filter 142 should be removed.

In some embodiments, the controller 170 may also be configured todetermine a pressure drop across the second filter 142. For example, asecond filter pressure sensor 148 may be operably coupled to the secondfilter 142 and configured to determine a pressure drop thereacross. Thecontroller 170 may be configured to interpret a pressure signal from thesecond filter pressure sensor 148 to determine a pressure drop acrossthe second filter 142. In response to the pressure drop being greaterthan a predetermined pressure threshold (e.g., corresponding to secondfilter 142 being substantially clogged or a high back pressure exertedon the exhaust gas), the controller 170 generates the fault code.

In particular embodiments, the aftertreatment system 100 may alsoinclude a hydrocarbon (HC) insertion assembly 122 configured to inserthydrocarbons into the exhaust gas flow path on, or upstream of theoxidation catalyst 130. The inserted hydrocarbons are oxidized on theoxidation catalyst 130 and serve to increase the temperature of theexhaust gas to a temperature sufficient to oxidize PM trapped in thefirst and/or second filters 140 and 142 so as to regenerate the firstand/or second filters 140 and 142.

For example, the filters 140 and/or 142 may become increasingly cloggedwith PM over time. This may increase filtration efficiency of the firstand/or second filters 140 and 142 by reducing a porosity of the filters140 and 142 as previously described herein, but also cause an increasein backpressure on the exhaust gas which reduces fuel efficiency. If notregenerated, the filters 140 and 142 may eventually become completelyblocked with PM or the backpressure can become sufficiently high so asto crack the first and/or second filter 140 and 142. In someembodiments, the hydrocarbon insertion assembly 122 may be activated toinsert hydrocarbons into the exhaust gas, for example, into or upstreamof the oxidation catalyst 130, in response to a backpressure of theexhaust gas increasing beyond a predetermined pressure threshold whichmay correspond to an amount of clogging of the first and/or secondfilter 140 and 142. For example, the controller 170 may activate thehydrocarbon insertion assembly 122 in response to the pressure dropacross the second filter 142 being greater than a predetermined pressurethreshold. The hydrocarbons may combust in the exhaust gas, therebyincreasing a temperature of the exhaust gas above a temperaturethreshold sufficient to oxidize PM trapped in the first and/or secondfilters 140 and 142 so as to regenerate the filters 140 and/or 142. Forexample, the second filter 142 may be regenerated before removal fromthe aftertreatment system 100.

FIG. 2 is a schematic flow diagram of a method 200 for controllingfiltration efficiency of an aftertreatment system (e.g., theaftertreatment system 100) as fuel economy of an engine producing anexhaust gas flowing through the aftertreatment system, according to anembodiment. The aftertreatment system includes an SCR system (e.g., theSCR system 150) a first filter (e.g., the first filter 140) positionedupstream of the SCR system and a second filter (e.g., the second filter142) positioned downstream of the first filter, for example, between thefirst filter and the SCR system or downstream of the SCR system. Thesecond filter may have a smaller pore size than the first filter, aspreviously described herein with respect to the aftertreatment system100.

The method 200 comprises determining a filtration efficiency of thefirst filter during operation of the aftertreatment system, at 202. Forexample, the filtration efficiency of the first filter 140 is determinedby the controller 170. In some embodiments, the method 200 may alsoinclude determining a first pressure drop across the first filter, and aflow rate of the exhaust gas downstream of the first filter (e.g., bythe controller 170). The filtration efficiency may be based on the firstpressure drop and the flow rate of the exhaust gas, for example, a ratioof the pressure drop to the flow rate.

At 204, it is determined if the first filtration efficiency is equal toor greater than a first filtration efficiency threshold. In response tothe first filtration efficiency of the first filter being equal to orgreater the first filtration efficiency threshold (204:YES), the method200 includes instructing a user to remove the second filter from theaftertreatment system, at 206. For example, as exhaust gas flows throughthe first filter 140, PM accumulates in the first filter 140 reducingits porosity and increasing its filtration efficiency. Once the firstfiltration efficiency of the first filter 140 reaches the firstfiltration efficiency threshold, corresponding to a desired filtrationefficiency from the first filter 140, the first filter 140 may besufficient to provide a desired filtration efficiency from theaftertreatment system 100 for meeting PM emission standards without thesecond filter 142. The user may be instructed via an audio signal (e.g.,an alarm), a video signal (e.g., lighting an indicator lamp on adashboard) or via a fault code (e.g., second filter remove code)generated by the controller 170, the fault code being available to theuser on demand.

In some embodiments, the method 200 may also include determining asecond pressure drop across the second filter in response to the firstfiltration efficiency being less than the filtration efficiencythreshold, at 208. If the pressure drop across the second filter is lessthan a predetermined pressure drop threshold at 210, the method 200returns to operation 202. In response to the second pressure drop beinggreater than a predetermined pressure drop threshold, in someembodiments, a regeneration of at least the second filter may beinitiated, at 212. For example, the second filter 142 and optionally,also the first filter 140 may be heated above a regeneration temperature(e.g., via a heater coupled to the second filter 142 and/or the firstfilter 140 or flowing exhaust gas at a temperature greater than theregeneration through the aftertreatment system 100) to oxidize theaccumulated PM (e.g., soot) in the second filter 142 and, in someembodiments, also the first filter 140. The method then returns tooperation 210. If it is determined that the second pressure drop isstill greater than the predetermined pressure drop, the user isinstructed to remove the second filter, at 214. For example, the secondpressure drop being above the predetermined pressure drop threshold maycorrespond to high back pressure exerted on the exhaust gas which mayreduce a fuel economy of the engine producing the exhaust gas below adesirable level or damage the second filter 142.

In some embodiments, the second filter 142 may be rotatably mountedwithin the housing 101 and configured to rotate between a firstconfiguration in which the second filter 142 is positioned within theexhaust gas flow path and a second configuration in which the secondfilter 142 rotated within the housing 101 to provide a flow path for theexhaust gas to bypass the second filter 142. For example, a biasingmember (e.g., a spring) may be coupled to the second filter 142 andconfigured to bias the second filter 142 into the first configuration tocause the exhaust gas to flow through the second filter 142. As thesecond filter 142 gets increasing clogged, a pressure of the exhaust gason the second filter 142 increases due to the decreasing porosity of thesecond filter 142. Once the pressure of the exhaust gas is equal to orgreater than a predetermined pressure threshold which may occur afterthe first filter 140 has reached its filtration efficiency threshold,the pressure may be sufficient to overcome the biasing force of thebiasing member to move the second filter 142 into the secondconfiguration. This allows the exhaust gas to bypass the second filter142, therefore reducing the backpressure on the exhaust gas andincreasing fuel economy. This may obviate removing of the second filter142 from the housing 101.

In other embodiments, the aftertreatment system 100 may also include abypass conduit (not shown) such as the bypass conduit 345 described withrespect to FIG. 3A, fluidly coupling an exhaust gas flow path of theexhaust gas downstream of the first filter 140 and upstream of thesecond filter 142 to an exhaust gas flow path downstream of the secondfilter 142. A pressure activated valve may be disposed in the bypassconduit and may be configured to open in response to a pressure of theexhaust gas exceeding a predetermined pressure threshold, for example,due to the porosity of the second filter 142 dropping too low, aspreviously described herein. The pressure activated valve may closeagain after the second filter is regenerated, and the cycle is repeated.

FIG. 3A is a schematic illustration of an aftertreatment system 300,according to yet another embodiment. The aftertreatment system 300 isconfigured to receive an exhaust gas from an engine (e.g., a dieselengine, a gasoline engine, a natural gas engine, a dual fuel engine, abiodiesel engine, an E-85 engine, or any other suitable engine) andreduce constituents of the exhaust gas such as, for example, NOx gases,CO, hydrocarbons, etc. The aftertreatment system 300 may comprise thereductant storage tank 110, the reductant insertion assembly 120, ahousing 301, the first filter 140, the second filter 142 and the SCRsystem 150, as previously described herein with respect to theaftertreatment system 100.

The housing 301 defines an internal volume within which the componentsof the aftertreatment system 300, i.e., the first filter 140, the secondfilter 142 and the SCR system 150 are positioned, as previouslydescribed herein. An inlet conduit 302 is fluidly coupled to an inlet ofthe housing 101 and structured to receive exhaust gas from the engineand communicate the exhaust gas to an internal volume defined by thehousing 301. Furthermore, an outlet conduit 304 may be coupled to anoutlet of the housing 301 and structured to expel treated exhaust gasinto the environment (e.g., treated to remove PM such as soot and ash bythe first and/or second filters 140 and 142 and/or reduce constituentsof the exhaust gas such as NOx gases included in the exhaust gas). Thefirst sensor 103 may be positioned in the inlet conduit 302 and thesecond sensor 105 may be positioned in the outlet conduit 304, aspreviously described herein with respect to the aftertreatment system100.

In some embodiments, the aftertreatment system 300 may also include theoxidation catalyst 130 (e.g., a diesel oxidation catalyst) disposedupstream of the first filter 140, for example, in the housing 301. Thehydrocarbon insertion assembly 122 may be configured to inserthydrocarbons (e.g., fuel such as diesel) into the exhaust gas upstreamof or on the oxidation catalyst 130 to a raise a temperature of theexhaust gas, for example, for regenerating the first filter 140 and/orthe second filter 142.

The first filter 140 is disposed upstream of the SCR system 150 and thesecond filter 142 is disposed downstream of the first filter 140, forexample, downstream of the SCR system 150 as shown in FIG. 3A. Forexample, insertion of the reductant into the SCR system 150 may resultin significant amount of solid particles (e.g., reductant particles,soot, ash, etc.) being present in the exhaust gas downstream of the SCRsystem 150, and positioning the second filter 142 downstream of the SCRsystem 150 may allow capture of such particles downstream of the SCRsystem 150. In other embodiments, the second filter 142 may be disposedupstream of the SCR system 150. A pressure sensor 346 (e.g., adifferential or delta pressure sensor) is operatively coupled to thesecond filter 142 and is configured to determine a pressure drop acrossthe second filter 142. The pressure drop may indicate a degree ofclogging of the second filter 142. The first filter 140 and the secondfilter 142 have the same structure and function as described withrespect to the aftertreatment system 100.

The aftertreatment system 300 also comprises a bypass conduit 345fluidly coupling an exhaust gas flow path of the exhaust gas downstreamof the first filter 140 and upstream of the second filter 142 to anexhaust gas flow path downstream of the second filter 142. For example,the bypass conduit 345 may fluidly a couple a volume of the housing 301located between the SCR system 150 and the second filter 142 to a volumeof the housing 301 downstream of the second filter 142. The bypassconduit 345 therefore provides a bypass flow path for the exhaust gas tobypass the second filter 142.

A valve 344 is operatively coupled to the bypass conduit 345. The valve344 may include a butterfly valve, a rotation valve, a diaphragm valve,a needle valve, a pinch valve, a check valve or any other suitablevalve. The valve 344 is moveable between a closed position in which theexhaust gas flows through the second filter 142, and an open position inwhich at least a portion of the exhaust gas flows through the bypassconduit 345 so as to bypass the second filter 142. In variousembodiments, a degree of opening of the valve 344 may be adjusted tocontrol an amount of exhaust gas flowing through the second filter 142and the amount of exhaust gas bypassing the second filter 142. Forexample, the valve 344 may be initially closed when the first filter 140is new or is recently regenerated to cause the exhaust gas to flowthrough the second filter 142 and provide high filtration efficiency.Over time, the first filter 140 gets increasingly clogged with PM andexperiences an increase in its first filtration efficiency. Furthermore,the second filter 142 also gets increasingly clogged as previouslydescribed herein with respect to the aftertreatment system 100 causingan increasing in backpressure on the exhaust gas which may reduce fueleconomy of the engine producing the exhaust gas. The valve 344 maytherefore, be increasingly opened to cause at least a portion of theexhaust gas to bypass the second filter 142 through the bypass conduit345 so as to reduce a back pressure on the exhaust gas. The valve 344may be completely opened once a first filtration efficiency of the firstfilter 140 has reached a first filtration efficiency thresholdcorresponding to a desired filtration efficiency from the aftertreatmentsystem 300 and/or a pressure drop across the second filter 142 isgreater than a pressure drop threshold.

While FIG. 3A shows the bypass conduit and the small pore size secondfilter 142 positioned downstream of the larger pore size first filter140, in other embodiments, a bypass conduit may be positioned across theupstream, filter alternatively, or additionally to the bypass conduitpositioned around the downstream filter. For example, FIG. 3B is aschematic block diagram of an aftertreatment system 300 b, according toanother embodiment. The aftertreatment system 300 b is similar to theaftertreatment system 300 with the following differences.

The aftertreatment system 300 b includes a first filter 140 b and asecond filter 142 b positioned downstream of the first filter 140 b. Afirst bypass conduit 345 b fluidly couples an exhaust gas flow pathupstream of the first filter 140 b to an exhaust gas flow path betweenthe first filter 140 b and the second filter 142 b. A first bypassconduit 345 b is operably coupled to the first bypass valve 344 b.Furthermore, a second bypass conduit 365 b fluidly couples an exhaustgas flow path between the first filter 140 b and the second filter 142b, to an exhaust gas flow path downstream of the second filter 142 b.The first valve 344 b and the second valve 364 b may be selectivelyopened or closed to cause a larger portion of the exhaust gas to flowthrough the first filter 140 b (first valve 344 b closed and secondvalve 364 b open), a larger portion of the exhaust gas to flow throughthe second filter 142 b (first valve 344 b open and second valve 364 bclosed) or the exhaust gas to flow through each of the filters 140 b and142 b (both valve 344 b and 364 b closed).

In some embodiments, the first filter 140 b may have a smaller pore sizeand therefore, a higher filtration efficiency than the second filter 142b. In such embodiments, the second bypass conduit 365 b may be excludedsuch that a degree of opening of the first valve 344 b may be controlledto provide high fuel economy or high filtration efficiency, as describedherein. Furthermore, the first filter 140 b may have a smaller diameterthan the second filter 142 b. In other embodiments, the second filter142 b may have a higher filtration efficiency than the first filter 140b to provide high filtration efficiency or fuel economy, as previouslydescribed with respect to FIG. 3A.

Referring again to FIG. 3A, a controller 370 may be operatively coupledto the valve 344 and configured to move the valve 344 into an openposition, a closed position or control a degree of opening of the valve344 so as to a control a ratio of the exhaust gas flowing through thesecond filter 142 or the bypass conduit 345. In some embodiments, thecontroller 370 may also be communicatively coupled to the first sensor103, the second sensor 105 and/or the pressure sensor 346. In someembodiments, the controller 370 may also be communicatively coupled tothe engine and configured to determine one or more engine operatingparameters (e.g., engine speed, engine torque, exhaust gas flow rate,fuel insertion rate, intake air flow rate, etc.) associated with theengine. The controller 370 may be operatively coupled to thesecomponents using any type and any number of wired or wirelessconnections. For example, a wired connection may include a serial cable,a fiber optic cable, a CAT5 cable, or any other form of wiredconnection. Wireless connections may include the Internet, Wi-Fi,cellular, radio, Bluetooth, ZigBee, etc. In one embodiment, a controllerarea network (CAN) bus provides the exchange of signals, information,and/or data. The CAN bus includes any number of wired and wirelessconnections.

In some embodiments, the controller 370 may be configured to determinean operating condition of the engine. For example, the controller 370may be configured to receive an engine signal from the engine, a firstsensor signal from the first sensor 103 and/or a second sensor signalfrom the second sensor 105 to determine an operating condition of theengine, for example, is the engine operating under a high PM operatingcondition in which a higher amount of PM is included in the exhaust gasemitted by the engine (e.g., during high engine load conditions) or alow PM operating condition in which a lower PM is included in theexhaust gas relative to the high PM operating condition (e.g., operatingunder steady state or low load conditions).

The controller 370 is configured to control the valve 344 such that thevalve 344 is more closed during the high particulate matter operatingcondition of the engine than during the low particulate matter operatingcondition of the engine, such that a larger portion of the exhaust gasflows through the second filter 142 during the high particulate matteroperating condition of the engine than during the low particulate matteroperating condition of the engine. For example, in response to theengine operating under a high PM operating condition, the controller 370may be configured to cause the valve 344 to open a first predeterminedamount such that the valve 344 is more closed than open so as to cause alarger portion of the exhaust gas to flow through the second filter 142than the bypass conduit 345 and provide high filtration efficiency. Whenthe engine is operating under the high PM operating condition, thecontroller 370 may completely close the valve 344 or open the valve 344a small degree to cause a larger portion of the exhaust gas to flowthrough the second filter 142 than the bypass conduit 345. The secondfilter 142 increases the filtration efficiency, as previously describedherein. In some embodiments, the high PM operating condition correspondsto a larger amount of reductant being inserted into the SCR system 150relative to the low PM operating condition.

In contrast, in response to the engine operating under a low PMoperating condition, the controller 370 may be configured to cause thevalve 344 to open a second predetermined amount such that the valve 344is more open than closed so as to cause a larger portion of the exhaustgas to flow through the bypass conduit 345 and provide high fueleconomy. For example, when the engine is operating under the low PMoperating condition, the controller 370 may be configured to open thevalve 344 a larger degree or completely open the valve 344 so as tocause a larger portion or substantially all of the exhaust gas to bypassthe second filter 142 via the bypass conduit 345. As previouslydescribed herein, as the second filter 142 becomes increasingly clogged,a backpressure on the exhaust gas increases which reduces fuel economy.If the filtration efficiency desired from the aftertreatment system 300is being met (e.g., due to the first filter 140 reaching the firstfiltration efficiency threshold), then allowing a larger portion of theexhaust gas to bypass the second filter 142 reduces the backpressure onthe exhaust gas and increases fuel economy. The valve 345 is controlledthat the exhaust gas expelled into the environment from theaftertreatment system 300 has a PM count which is lower than apredetermined threshold, for example, to meet an emission standard.Thus, regardless of the high PM or low PM operating condition, thecontroller 370 is configured to ensure that the exhaust gas emitted fromthe aftertreatment system 300 meets a desired emission standard.

In some embodiments, the controller 370 may be configured to determinean operating condition of the aftertreatment system 300 (e.g., apressure drop across the first filter 140, a filtration efficiency ofthe first filter 140, a pressure drop across the second filter 142, aflow rate and/or temperature of the exhaust gas) and open or close thevalve 344 based on the operating condition of the aftertreatment system300.

The controller 370 may be configured to determine whether a firstfiltration efficiency of the first filter 140 is less than or equal to afirst filtration efficiency threshold or greater than the firstfiltration efficiency threshold. The controller 370 is configured tocontrol the valve 344 such that the valve 344 is more closed when thefirst filtration efficiency is less than or equal to the firstfiltration efficiency threshold than when the first filtrationefficiency is greater than the first filtration efficiency threshold,such that a larger portion of the exhaust gas flows through the secondfilter 142 when the first filtration efficiency is less than the firstfiltration efficiency threshold. For example, the valve 344 may beinitially in the closed position when the first filtration efficiency isless than or equal to the first filtration efficiency threshold suchthat substantially all of the exhaust gas flows through the secondfilter 142. In response to the first filtration efficiency being greaterthan a first filtration efficiency threshold, the controller 370increasingly opens the valve 344 so that the valve is less closedrelative to when the first filtration efficiency is less than or equalto the first filtration efficiency threshold and more of the exhaust gasflows through the bypass conduit 345 than the second filter 142.

Expanding further, in some embodiments, the controller 370 is configuredto determine a first filtration efficiency of the first filter 140. Ifthe first filtration efficiency is less than a first filtrationefficiency threshold, the controller 370 closes the valve 344 to causethe exhaust gas to flow through the second filter 142 so as to providehigh filtration efficiency. In response to the first filtrationefficiency being equal to or greater than the first filtrationefficiency threshold, the controller 370 may increase opening of thevalve 344 (e.g., completely open the valve 344) such that at least aportion of the exhaust gas bypasses the second filter 142 via the bypassconduit 345. As previously described herein, the valve 345 is controlledthat the exhaust gas expelled into the environment from theaftertreatment system 300 has a PM count which is lower than apredetermined threshold, for example, to meet the emission standard.

In some embodiments, the controller 370 may be configured to determine afirst pressure drop across the first filter 140. For example, a firstpressure sensor 348 may be operatively coupled to the first filter 140and configured to determine a pressure drop across the first filter 140.The controller 370 may be operatively coupled to the first pressuresensor 348 and configured to determine a first pressure dropthereacross. The controller 370 may also be configured to determine aflow rate of the exhaust gas. The controller 370 may be configured todetermine a first filtration efficiency of the first filter 140 based onthe first pressure drop and the flow rate of the exhaust gas, forexample, a ratio between the pressure drop (e.g., differential pressure)and the flow rate.

For example, FIG. 5 shows a plot of filtration efficiency of a firstfilter vs. a flow restriction (i.e., a ratio of pressure drop across thefirst filter and a flow rate of the exhaust gas) across the firstfilter, according to a specific embodiment. As exhaust gas continues toflow through the first filter 140, a PM load, for example, a soot loador an ash load on the first filter 140 continues to increase causing acorresponding increase in the filtration efficiency of the first filter(e.g., the first filter 140) until the first filtration efficiencyreaches a first filtration efficiency threshold (e.g., greater than 95%filtration efficiency). In some embodiments, the first filtrationefficiency threshold corresponds to a ash load of 0.1-10 g/L on thefirst filter 140 for a mileage of the engine producing the exhaust ofless than 5,000 miles. For example, as shown in FIG. 5, for a particularfirst filter, the first filtration efficiency threshold corresponds to a0.25 g/L soot load or equivalent 2 g/L ash load on the first filter, atwhich the first filtration efficiency is close to 100%. It should beappreciated that in other embodiments, the first filtration efficiencythreshold may be different depending on the particular first filter usedin the aftertreatment system 300.

In some embodiments, the controller 370 may also be configured todetermine a pressure drop across the second filter 142. For example, thecontroller 370 may receive a pressure signal from the pressure sensor346 and determine the pressure drop across the second filter 142therefrom. In response to the pressure drop being greater than apredetermined pressure drop threshold, the controller 370 may beconfigured to open the valve 344 so as to allow at least a portion ofthe exhaust gas to bypass the second filter 142 via the bypass conduit345. For example, the pressure drop across the second filter 142 beinggreater than a predetermined pressure drop threshold may correspond to ahigh backpressure on the exhaust gas which reduces fuel economy below afuel economy threshold. Thus, the controller 370 opens the valve 344 soas to allow at least a portion of the exhaust gas to bypass the secondfilter 142 and reduce back pressure on the exhaust gas. In someembodiments, the controller 370 may be configured to open the valve 344if the second filter 142 is difficult to regenerate or a temperature ofthe exhaust gas reaching the second filter 142 is below a predeterminedtemperature threshold which may correspond to the pressure drop acrossthe second filter 142 being greater than the predetermined pressure dropthreshold.

In some embodiments, the controller 370 may also be configured todetermine a temperature of the exhaust gas proximate to an inlet of thesecond filter 142. For example, the controller 370 may becommunicatively coupled to a temperature sensor 341 positioned upstreamof the second filter 142 and receive a temperature signal therefromcorresponding to a temperature of the exhaust gas at the inlet of thesecond filter 142. In response to the temperature of the exhaust gasbeing above the predetermined temperature threshold, the controller 370may be configured to close the valve 344 so as to force hot exhaust gasto flow through the second filter 142 for regenerating the second filter142. In some embodiments, the controller 370 may also be communicativelycoupled to the hydrocarbon insertion assembly 122 and configured toinstruct the hydrocarbon insertion assembly 122 to insert hydrocarbonsinto the oxidation catalyst 130 for raising the temperature of theexhaust gas above the predetermined temperature threshold, for example,for regenerating the first filter 140 and/or the second filter 142.

In particular embodiments, the controller 370 may be included in acontrol circuitry. For example, FIG. 4 is a schematic block diagram of acontrol circuitry 371 that comprises the controller 370, according to anembodiment. The controller 370 comprises a processor 372, a memory 374,or any other computer readable medium, and a communication interface376. Furthermore, the controller 370 includes an engine operatingcondition determination circuitry 374 a, a pressure and flow ratedetermination circuitry 374 b, a temperature determination circuitry 374c and a valve control circuitry 374 d. It should be understood that thecontroller 370 shows only one embodiment of the controller 370 and anyother controller capable of performing the operations described hereincan be used.

The processor 372 can comprise a microprocessor, programmable logiccontroller (PLC) chip, an ASIC chip, or any other suitable processor.The processor 372 is in communication with the memory 374 and configuredto execute instructions, algorithms, commands, or otherwise programsstored in the memory 374.

The memory 374 comprises any of the memory and/or storage componentsdiscussed herein. For example, memory 374 may comprise a RAM and/orcache of processor 372. The memory 374 may also comprise one or morestorage devices (e.g., hard drives, flash drives, computer readablemedia, etc.) either local or remote to controller 370. The memory 374 isconfigured to store look up tables, algorithms, or instructions.

In one configuration, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d are embodied as machine or computer-readable media(e.g., stored in the memory 374) that is executable by a processor, suchas the processor 372. As described herein and amongst other uses, themachine-readable media (e.g., the memory 374) facilitates performance ofcertain operations to enable reception and transmission of data. Forexample, the machine-readable media may provide an instruction (e.g.,command, etc.) to, e.g., acquire data. In this regard, themachine-readable media may include programmable logic that defines thefrequency of acquisition of the data (or, transmission of the data).Thus, the computer readable media may include code, which may be writtenin any programming language including, but not limited to, Java or thelike and any conventional procedural programming languages, such as the“C” programming language or similar programming languages. The computerreadable program code may be executed on one processor or multipleremote processors. In the latter scenario, the remote processors may beconnected to each other through any type of network (e.g., CAN bus,etc.).

In another configuration, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d are embodied as hardware units, such as electroniccontrol units. As such, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d may be embodied as one or more circuitry componentsincluding, but not limited to, processing circuitry, network interfaces,peripheral devices, input devices, output devices, sensors, etc.

In some embodiments, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d may take the form of one or more analog circuits,electronic circuits (e.g., integrated circuits (IC), discrete circuits,system on a chip (SOCs) circuits, microcontrollers, etc.),telecommunication circuits, hybrid circuits, and any other type of“circuit.” In this regard, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d may include any type of component for accomplishing orfacilitating achievement of the operations described herein. Forexample, a circuit as described herein may include one or moretransistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR,etc.), resistors, multiplexers, registers, capacitors, inductors,diodes, wiring, and so on.

Thus, the engine operating condition determination circuitry 374 a, thepressure and flow rate determination circuitry 374 b, the temperaturedetermination circuitry 374 c and the valve control circuitry 374 d mayalso include programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices or thelike. In this regard, the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d may include one or more memory devices for storinginstructions that are executable by the processor(s) of the engineoperating condition determination circuitry 374 a, the pressure and flowrate determination circuitry 374 b, the temperature determinationcircuitry 374 c and the valve control circuitry 374 d. The one or morememory devices and processor(s) may have the same definition as providedbelow with respect to the memory 374 and the processor 372.

In the example shown, the controller 370 includes the processor 372 andthe memory 374. The processor 372 and the memory 374 may be structuredor configured to execute or implement the instructions, commands, and/orcontrol processes described herein with respect the engine operatingcondition determination circuitry 374 a, the pressure and flow ratedetermination circuitry 374 b, the temperature determination circuitry374 c and the valve control circuitry 374 d. Thus, the depictedconfiguration represents the aforementioned arrangement where the engineoperating condition determination circuitry 374 a, the pressure and flowrate determination circuitry 374 b, the temperature determinationcircuitry 374 c and the valve control circuitry 374 d are embodied asmachine or computer-readable media. However, as mentioned above, thisillustration is not meant to be limiting as the present disclosurecontemplates other embodiments such as the aforementioned embodimentwhere the engine operating condition determination circuitry 374 a, thepressure and flow rate determination circuitry 374 b, the temperaturedetermination circuitry 374 c and the valve control circuitry 374 d, orat least one circuit of the engine operating condition determinationcircuitry 374 a, the pressure and flow rate determination circuitry 374b, the temperature determination circuitry 374 c and the valve controlcircuitry 374 d are configured as a hardware unit. All such combinationsand variations are intended to fall within the scope of the presentdisclosure.

The processor 372 may be implemented as one or more general-purposeprocessors, an application specific integrated circuit (ASIC), one ormore field programmable gate arrays (FPGAs), a digital signal processor(DSP), a group of processing components, or other suitable electronicprocessing components. In some embodiments, the one or more processorsmay be shared by multiple circuits (e.g., the engine operating conditiondetermination circuitry 374 a, the pressure and flow rate determinationcircuitry 374 b, the temperature determination circuitry 374 c and thevalve control circuitry 374 d) may comprise or otherwise share the sameprocessor which, in some example embodiments, may execute instructionsstored, or otherwise accessed, via different areas of memory).Alternatively or additionally, the one or more processors may bestructured to perform or otherwise execute certain operationsindependent of one or more co-processors. In other example embodiments,two or more processors may be coupled via a bus to enable independent,parallel, pipelined, or multi-threaded instruction execution. All suchvariations are intended to fall within the scope of the presentdisclosure. The memory 374 (e.g., RAM, ROM, Flash Memory, hard diskstorage, etc.) may store data and/or computer code for facilitating thevarious processes described herein. The memory 374 may be communicablyconnected to the processor 372 to provide computer code or instructionsto the processor 372 for executing at least some of the processesdescribed herein. Moreover, the memory 374 may be or include tangible,non-transient volatile memory or non-volatile memory. Accordingly, thememory 374 may include database components, object code components,script components, or any other type of information structure forsupporting the various activities and information structures describedherein.

The communication interface 376 may include wireless interfaces (e.g.,jacks, antennas, transmitters, receivers, communication interfaces, wireterminals, etc.) for conducting data communications with varioussystems, devices, or networks. For example, the communication interface376 may include an Ethernet card and port for sending and receiving datavia an Ethernet-based communications network and/or a Wi-Ficommunication interface for communicating with, for example, the firstsensor 103, the second sensor 105, the engine, the valve 344, thepressure sensor 346, the first pressure sensor 348, the hydrocarboninsertion assembly 122 and/or any other component of the aftertreatmentsystem 300. The communication interface 376 may be structured tocommunicate via local area networks or wide area networks (e.g., theInternet, etc.) and may use a variety of communications protocols (e.g.,IP, LON, Bluetooth, ZigBee, radio, cellular, near field communication,etc.).

The engine operating condition determination circuitry 374 a may beconfigured to receive an engine operating condition signal, for example,from the engine, the first and/or second sensors 103 and 105 or anyother sensor and determine if the engine is operating under a high PMoperating condition or a low PM operating condition. Furthermore, theengine operating condition determination circuitry 374 a may also beconfigured to determine an aftertreatment operating condition signal,for example, from the pressure sensors 346 and/or 348, from thetemperature sensor 341, the first sensor 103 and/or the second sensor105.

The valve control circuitry 374 d is configured to generate a valvesignal configured to open the valve 344, close the valve 344 or adjust adegree of opening of the valve 344, as previously described herein. Inresponse to the engine operating under the high PM operating condition,the valve control circuitry 374 d may be configured to cause the valve344 to open the first predetermined amount such that the valve 344 ismore closed than open or completely close the valve 344 to increase afiltration efficiency of the aftertreatment system 300, as previouslydescribed herein. Furthermore, in response to the engine operating underthe low PM operating condition, the valve control circuitry 374 d may beconfigured to cause the valve 344 to open the second predeterminedamount such that the valve 344 is more open than closed or completelyopen the valve 344 to increase a fuel economy of the engine, aspreviously described herein.

The pressure and flow rate determination circuitry 374 b is configuredto determine a first pressure drop across the first filter 140 (e.g.,from a pressure signal received from the first pressure sensor 348) anddetermine a flow rate of the exhaust gas (e.g., from a flow rate signalreceived from a flow rate sensor or based on one or more engineoperating conditions). The pressure and flow rate determinationcircuitry 374 b may determine a first filtration efficiency of the firstfilter 140 based on the first pressure drop and the exhaust gas flowrate (e.g., a ratio of the pressure drop to the exhaust gas flow rate).In response to the first filtration efficiency being equal to or greaterthan the first filtration efficiency threshold, the valve controlcircuitry 374 d may increase opening of the valve 344 or otherwisecompletely open the valve 344.

In some embodiments, the pressure and flow rate determination circuitry374 b may also be configured to determine a pressure drop across thesecond filter 142 (e.g., from a pressure signal received from thepressure sensor 346). In response to the pressure drop across the secondfilter 142 being greater than a predetermined pressure drop threshold,the valve control circuitry 374 d may be configured to open the valve344 so as to allow at least a portion of the exhaust gas to bypass thesecond filter 142, as previously described herein.

The temperature determination circuitry 374 c may be configured todetermine a temperature of the exhaust gas proximate to the inlet of thesecond filter 142 (e.g., from a temperature signal received from thetemperature sensor 341). In response, to the temperature of the exhaustgas being above the predetermined temperature threshold, the valvecontrol circuitry 374 d may be configured to close the valve 344 (e.g.,by the second predetermined amount or completely close the valve 344) soas to force hot exhaust gas to flow through the second filter 142 forregenerating the second filter 142, as previously described herein. Insome embodiments, the temperature determination circuitry 374 c may alsobe configured to instruct the hydrocarbon insertion assembly 122 toinsert hydrocarbons into the oxidation catalyst 130 or the exhaust gasto raise a temperature of the exhaust gas to the predeterminedtemperature threshold for regenerating the first and/or second filters140 and 142.

FIG. 6 is a schematic illustration of an aftertreatment system 400,according to another embodiment. The aftertreatment system 400 isconfigured to receive an exhaust gas from an engine (e.g., a dieselengine, a gasoline engine, a natural gas engine, a dual fuel engine, abiodiesel engine, an E-85 engine, or any other suitable engine) andreduce constituents of the exhaust gas such as, for example, NOx gases,CO, hydrocarbons, etc. The aftertreatment system 400 may comprise thereductant storage tank 110, the reductant insertion assembly 120, ahousing 401, the first filter 140, a second filter 442 disposeddownstream of the first filter 140, the SCR system 150 disposeddownstream of the second filter 442, and the controller 370 aspreviously described herein with respect to the aftertreatment system100, 300. In other embodiments, the second filter 442 may be disposeddownstream of the SCR system 150. In some embodiments, theaftertreatment system 400 may also include the oxidation catalyst 130disposed upstream of the first filter 140, and the hydrocarbon insertionassembly 122 for selectively inserting hydrocarbons into the exhaustgas, as previously described herein.

The housing 401 includes an inlet conduit 402 having the first sensor103 disposed therein, and an outlet conduit 404 having the second sensor105 disposed therein. The second filter 442 may have a smaller diameterthan the first filter 140 or otherwise a diameter of the housing 401such that a bypass conduit 445 is defined around the second filter 442between an outer radial surface of the second filter 442 and an innerradial surface of the housing 401. The second filter 442 may have asmaller pore size and, thereby a higher filtration efficiency than thefirst filter 140, and may be similar in function to the second filter142, as previously described herein. The pressure sensor 346 may beoperatively coupled to the second filter 442 and configured to determinea pressure drop across the second filter 442. Furthermore, thetemperature sensor 341 may be positioned upstream of the second filter442 and configured to determine a temperature of the exhaust gasentering the second filter 442.

A valve 460 is disposed at an inlet of bypass conduit 445 between theinner surface of the housing 401 and an outer surface of the secondfilter 442. The valve 460 is configured to be selectively opened tocontrol an amount of exhaust gas flowing through the second filter 442and/or around the second filter 442 through the bypass conduit 445. Forexample, the controller 370 may be operatively coupled to the valve 460and configured to open the valve 460, close the valve 460 or open thevalve 460 a predetermined amount, for example, to control an amount ofthe exhaust gas flowing through the second filter 442 and through thebypass conduit 445, as previously described herein.

In some embodiments, the valve 460 may include a ring type valve.Referring also now to FIGS. 7A-7B and 8A-8B, a portion of the housing401 is shown that includes the first filter 140, the second filter 442and the valve 460 positioned therebetween. As shown in FIG. 7B, thevalve 460 includes a plurality of rings including a first ring 462defining a plurality of first openings 464, for example, a plurality ofequally spaced slits defined through the first ring 462. The first ring462 defines a first diameter D1 at a first end 463 thereof proximate toan outlet of the first filter 140 and a second diameter D2 at a secondend 465 thereof proximate to an inlet of the second filter 442 which issmaller than the first diameter D1. The second diameter D2 may beapproximately equal to an outer diameter of the second filter 442. Thefirst end 463 may be coupled to an inner surface of the housing 401and/or an outer surface of the first filter 140, for example, to preventleakage of the exhaust gas therethrough between the housing 401 and thefirst end 463. Furthermore, the second end 465 may be coupled to theinlet of the second filter 442, for example, to prevent leakage of theexhaust gas between the second end 465 and the second filter 442. Invarious embodiments, the first ring 462 may be immovably disposed in thehousing 401.

The valve 460 also comprises a second ring 466 defining a plurality ofsecond openings 468, for example, a plurality of equally spaced slitsdefined through the second ring 466. The second ring 466 abuts the firstring 462 and is axially aligned therewith. The second ring 466 may besubstantially similar to the first ring 462 in size and shape.Furthermore, a radial spacing between the plurality of first openings464 and the plurality of second openings 468 may be approximately equalto each other.

The second ring 466 maybe rotatable relative to the first ring 462, forexample, in a scissor like motion, such that in a closed position of thevalve 460 (FIG. 8A), the plurality of first openings 464 are misalignedwith the plurality of second openings 468 such that the exhaust gasflows through the second filter 442. In the open position shown in FIG.8B, the second ring 466 is rotated relative to the first ring 462 tomove the valve 460 into the open position in which the plurality offirst openings 464 are aligned with the plurality of second openings 468such that a flow path is defined therethrough. More of the exhaust gasflows through the second filter 442 when the valve 460 is in the closedposition than when the valve 460 is in the open position. In someembodiments, at least a portion of the exhaust gas flows through theplurality of first and second openings 464 and 468 and through thebypass conduit 445 around the second filter 442 in the open position ofthe valve 460, thereby bypassing the second filter 442. In variousembodiments, an external rotational actuator with a cam may be used toprovide six degrees of rotation to the second ring 466 relative to thefirst ring 462 for opening or closing of the valve 460. The second ring466 may be variably rotated relative to the first ring 462 to controlthe amount of exhaust gas flowing through the second filter 442 vs. thebypass conduit 445.

While shown as including the first ring 462 and the second ring 466, inother embodiments, the valve 460 may include more than two rings, forexample, three rings or four rings each having predetermined spacetherebetween. With two rings, the valve 460 may have a 50% open frontalarea. In a three ring arrangement, two of the rings may be rotatablerelative to a third stationary and may be able to provide up to 66% openfrontal area. Similarly, in a four ring arrangement, at least two ofrings may be rotatable such that the valve may be able to provide up to75% open frontal area.

FIG. 9 is a schematic illustration of an aftertreatment system 500,according to an embodiment. The aftertreatment system 500 is configuredto receive an exhaust gas from an engine (e.g., a diesel engine, agasoline engine, a natural gas engine, a dual fuel engine, a biodieselengine, an E-85 engine, or any other suitable engine) and reduceconstituents of the exhaust gas such as, for example, NOx gases, CO,hydrocarbons, etc. The aftertreatment system 500 may comprise a housing501, the first filter 140, the SCR system 150 disposed downstream of thefirst filter 140, a second filter 542 disposed downstream of the SCRsystem 150, and the controller 370, as previously described herein withrespect. In other embodiments, the second filter 442 may be disposedupstream of the SCR system 150 and downstream of the first filter 140.In some embodiments, the aftertreatment system 500 may also include theoxidation catalyst 130 disposed upstream of the first filter 140.Furthermore, an ammonia slip catalyst may be disposed downstream of theSCR system 150.

The housing 501 includes an inlet conduit 502 having the first sensor103 disposed therein, and an outlet conduit 504 having the second sensor105 disposed therein. A reductant injector 582 may be disposed upstreamof the SCR system 150 and configured to insert reductant into theexhaust gas. In some embodiments, the aftertreatment system 500 may alsoinclude a mixer 580 disposed upstream of the SCR system 150 andconfigured to facilitate mixing of the reductant with the exhaust gas. Aplurality of temperature sensors T₁, T₂, T₃, T₄ and T₅ may be disposedat various locations along the housing 501 and configured to measure thetemperature of the exhaust gas at the respective locations. The firstpressure sensor 348 may be operatively coupled to the first filter 140and configured to determine a pressure drop thereacross, as previouslydescribed herein.

The second filter 542 is disposed downstream of the SCR system 150. Thesecond filter 542 may have a smaller pore size and, therefore a higherfiltration efficiency than the first filter 140, and may be similar infunction to the second filter 142, 442. The second filter 542 defines abypass conduit 545 therethrough, for example, through a longitudinalaxis thereof. A valve 544 (e.g., a butterfly valve) is disposed in thebypass conduit 545 and moveable between an open position and a closedposition. For example, the controller 370 may be configured to instructthe valve 544 to move into a closed position in response a high PMoperating condition of the engine, when the first filtration efficiencyof the first filter 140 is below the first filtration efficiencythreshold and/or if a pressure drop across the second filter 542 isbelow a predetermined pressure drop threshold. In response to a low PMengine operating condition, or a first filtration efficiency of thefirst filter 140 reaching the first filtration efficiency threshold, thecontroller 370 may be configured to open the valve 544 causing at leasta portion of the exhaust gas to flow through the bypass conduit 545defined through the second filter 542 so as to reduce back pressure onthe exhaust gas and increase fuel economy, as previously describedherein.

FIG. 10 is a plot of overall filtration efficiency vs. time of anaftertreatment system coupled to an engine operating at high engineload. The aftertreatment system includes a first filter having a firstfiltration efficiency and a second filter having a second filtrationefficiency greater than the first filtration efficiency. The secondfilter is positioned downstream of the first filter. For example, thefirst filter may be a new filter or a recently regenerated filter andthe first filtration efficiency may be lower than a first filtrationefficiency threshold which does not provide sufficient filtrationefficiency to meet a particle emissions standard desirable from theaftertreatment system.

The aftertreatment system also includes a bypass conduit (e.g., bypassconduit 345, 445, 545) having a valve (e.g., the valve 344, 460, 544)disposed thereon, and configured to allow at least a portion of theexhaust gas to bypass the second filter when the valve is open. As shownin FIG. 10, when the valve is open such that the exhaust gas or a largeportion of the exhaust gas bypasses the second filter, the overallfiltration efficiency of the aftertreatment system is about 50%corresponding to the first filtration efficiency, which may be below adesired filtration efficiency from the aftertreatment system. Incontrast, when the valve is closed, a large portion or substantially allof the exhaust gas is forced to flow through the second filter. In thisconfiguration, the overall filtration efficiency of the aftertreatmentsystem is about 100% corresponding to the filtration efficiency of eachof the first and second filters, as previously described herein. Thisshows that including the second filter in the aftertreatment system mayselectively increase the filtration efficiency of the aftertreatmentsystem by closing the valve, and may selectively increase a fuel economyof the engine by opening the valve to reduce a backpressure on theexhaust gas, as previously described herein.

FIGS. 11A-11B are schematic flow diagrams of a method 600 forcontrolling filtration efficiency and fuel economy of an aftertreatmentsystem, according to an embodiment. The aftertreatment system (e.g., theaftertreatment system 300, 400, 500) may include a first filter (e.g.,the first filter), a second filter (e.g., the second filter 142, 442,542) positioned downstream of the first filter, a bypass conduit (e.g.,the bypass conduit 345, 445, 545) fluidly coupling an exhaust gas flowpath downstream of the first filter and upstream of the second filter toan exhaust gas flow path downstream of the second filter and a valve(e.g., the valve 344, 460, 544) operatively coupled to the bypassconduit. In various embodiments, the aftertreatment system may alsoinclude a SCR system (e.g., the SCR system 150) positioned upstream ordownstream of the second filter.

The method 600 includes determining an operating condition of theengine, at 602. For example, the controller 370 may be configured toreceive a signal from the engine, the first sensor 103, the secondsensor 105, the pressure sensor 346 or the first pressure sensor 348 todetermine the operating condition of the engine. At 604, it isdetermined if the engine is operating under a high PM operatingcondition. In response, to the engine operating under the high PMoperating condition (604:YES) (or otherwise if a high filtrationefficiency is desired), the valve is opened a first predeterminedamount, at 606 such that the valve is more closed than open so as tocause a larger portion of the exhaust gas to flow through the secondfilter than the bypass conduit and provide high filtration efficiency.For example, the controller 370 may be configured to cause the valve344, 460, 544 to slightly open or be substantially closed so as to causea larger portion of the exhaust gas (e.g., substantially all of theexhaust gas) to flow through the second filter, therefore providing highfiltration efficiency.

In response to the engine operating under a low PM operating condition(604:NO) (or otherwise, if high fuel economy is desired), the valve isopened a second predetermined amount, at 608 such that the valve is moreopen than closed so as to cause a larger portion of the exhaust gas toflow through the bypass conduit and provide high fuel economy. Forexample, the controller 370 may cause the valve 344, 460, 544 to open alarge degree, for example, completely open so as to allow a largerportion of the exhaust gas (e.g., substantially all of the exhaust gas)to bypass the second filter (e.g., the second filter 142, 442, 542) viathe bypass conduit (e.g., the bypass conduit 345, 445, 545), thereforereducing backpressure on the exhaust gas and providing high fueleconomy.

In some embodiments, the method 600 also includes determining a firstfiltration efficiency of the first filter, at 610. For example, thecontroller 370 may determine a first pressure drop across the firstfilter 140, determine a flow rate of the exhaust gas, and determines thefirst filtration efficiency of the first filter 140 based on a pressuredrop across the first filter and an exhaust flow rate, as previouslydescribed herein.

At 612, it is determined if the first filtration efficiency exceeds apredetermined filtration efficiency threshold, for example, determinedby the controller 370. If the first filtration efficiency is less thanthe predetermined filtration efficiency threshold (612:NO), for example,corresponding to a desired filtration efficiency of the aftertreatmentsystem, the method 600 returns to operation 610. In response to thefirst filtration efficiency exceeding the predetermined filtrationefficiency threshold, the valve is opened a predetermined amount, at614, for example, completely opened to allow at least a portion orsubstantially all of the exhaust gas to bypass the second filter via thebypass conduit. This reduces backpressure on the exhaust gas andincreases fuel economy, while providing the desired filtrationefficiency via the first filter.

In some embodiments, the method 600 also includes determining a pressuredrop across the second filter, at 616. For example, the controller 370may interpret a signal from the pressure sensor 346 to determine apressure drop across the second filter. At 618, it is determined if thepressure drop exceeds a pressure drop threshold. The pressure drop maycorrelate to an amount of clogging corresponding to an amount of backpressure exerted on the exhaust gas. If the pressure drop is less thanthe pressure drop threshold (618:NO), the method returns to operation616. In response to the pressure drop being greater than thepredetermined threshold (e.g., corresponding to the exhaust gas backpressure being too high), the valve is opened (e.g. by the controller370) to allow at least a portion of the exhaust gas to bypass the secondfilter via the bypass conduit so as to decrease a back pressure on theexhaust gas.

In some embodiments, the method 600 also comprises determining atemperature of the exhaust gas proximate to an inlet of the secondfilter, at 622. For example, the controller 370 may be configured toreceive a temperature signal from the temperature sensor 341 andinterpret the temperature signal to determine the temperature of theexhaust gas at the inlet of the second filter. At 624, it is determinedif the temperature exceeds a predetermined temperature threshold. If thetemperature is lower than the predetermined temperature threshold, themethod 600 returns to operation 622. In response to the temperature ofthe exhaust gas being above or greater than the predeterminedtemperature threshold, the valve is closed so as to force hot exhaustgas to flow through the second filter for regenerating the filter. Forexample, the controller 370 may be configured to close the valve 344,460, 544 to force the exhaust gas through the second filter 142, 442,542 so as to regenerate the second filter. In some embodiments, in whichthe aftertreatment system includes a hydrocarbon insertion assembly(e.g., the hydrocarbon insertion assembly 122) the method may alsoinclude inserting hydrocarbons into an oxidation catalyst (e.g., theoxidation catalyst 130) for raising the temperature of the exhaust gasabove the predetermined temperature threshold.

In some embodiments, the controller 370, the control circuitry 371, orany of the controller or control circuitries described herein maycomprise a system computer of an apparatus or system which comprises theaftertreatment system 300, 400, 500 (e.g., a vehicle, an engine orgenerator set, etc.). For example, FIG. 12 is a block diagram of acomputing device 730 in accordance with an illustrative implementation.The computing device 730 can be used to perform any of the methods orthe processes described herein, for example, the method 200, or 600. Insome embodiments, the controller 370 may comprise the computing device730. The computing device 730 comprises a bus 732 or other communicationcomponent for communicating information. The computing device 730 canalso comprise one or more processors 734 or processing circuits coupledto the bus 732 for processing information.

The computing device 730 also comprises main memory 736, such as arandom access memory (RAM) or other dynamic storage device, coupled tothe bus 732 for storing information and instructions to be executed bythe processor 734. Main memory 736 can also be used for storing positioninformation, temporary variables, or other intermediate informationduring execution of instructions by the processor 734. The computingdevice 730 may further comprise ROM 738 or other static storage devicecoupled to the bus 732 for storing static information and instructionsfor the processor 734. A storage device 740, such as a solid-statedevice, magnetic disk or optical disk, is coupled to the bus 732 forpersistently storing information and instructions. For example,instructions corresponding operations of the method 200, 600 can bestored on the storage device 740. The computing device 730 may becoupled via the bus 732 to a display 744, such as a liquid crystaldisplay or active matrix display, for displaying information to a user.An input device 742, such as a keyboard or alphanumeric pad, may becoupled to the bus 732 for communicating information and commandselections to the processor 734.

According to various implementations, the methods described herein canbe implemented by the computing device 730 in response to the processor734 executing an arrangement of instructions contained in main memory736 (e.g., the operations of the method 200). Such instructions can beread into main memory 736 from another non-transitory computer-readablemedium, such as the storage device 740. Execution of the arrangement ofinstructions contained in main memory 736 causes the computing device730 to perform the illustrative processes described herein. One or moreprocessors in a multi-processing arrangement may also be employed toexecute the instructions contained in main memory 736. In alternativeimplementations, hard-wired circuitry may be used in place of or incombination with software instructions to effect illustrativeimplementations. Thus, implementations are not limited to any specificcombination of hardware and software.

Although an example computing device has been described in FIG. 12,implementations described in this specification can be implemented inother types of digital electronic, or in computer software, firmware, orhardware, including the structures disclosed in this specification andtheir structural equivalents, or in combinations of one or more of them.

Implementations described in this specification can be implemented indigital electronic, or in computer software, firmware, or hardware,including the structures disclosed in this specification and theirstructural equivalents, or in combinations of one or more of them. Theimplementations described in this specification can be implemented asone or more computer programs (i.e., one or more circuitries of computerprogram instructions) encoded on one or more computer storage media forexecution by, or to control the operation of, data processing apparatus.A computer storage medium comprises a non-transitory computer readablemedium and can be, or be included in, a computer-readable storagedevice, a computer-readable storage substrate, a random or serial accessmemory array or device, or a combination of one or more of them.Moreover, while a computer storage medium is not a propagated signal, acomputer storage medium can be a source or destination of computerprogram instructions encoded in an artificially-generated propagatedsignal. The computer storage medium can also be, or be included in, oneor more separate components or media (e.g., multiple disks, or otherstorage devices). Accordingly, the computer storage medium is bothtangible and non-transitory.

The operations described in this specification can be performed by adata processing apparatus on data stored on one or morecomputer-readable storage devices or received from other sources. Theterm “data processing apparatus” or “computing device” encompasses allkinds of apparatus, devices, and machines for processing data,including, by way of example, a programmable processor, a computer, asystem on a chip, or multiple ones, or combinations of the foregoing.The apparatus can comprise special purpose logic, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application-specific integratedcircuit). In addition to hardware, the apparatus can also comprise codethat creates an execution environment for the computer program inquestion (e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them). The apparatus and execution environment canrealize various different computing model infrastructures, such as webservices, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a circuitry, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or morecircuitries, sub-programs, or portions of code). A computer program canbe deployed to be executed on one computer, on multiple computers thatare located at one site, or distributed across multiple sites andinterconnected by a communication network.

Processors suitable for the execution of a computer program comprise, byway of example, both general and special purpose microprocessors and anyone or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also comprise, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data (e.g., magnetic, or flash drives). However, a computer neednot have such devices. Devices suitable for storing computer programinstructions and data comprise all forms of non-volatile memory, mediaand memory devices, including, by way of example, semiconductor memorydevices (e.g., EPROM, EEPROM, and flash memory devices) or magneticdisks (e.g., internal hard disks or removable disks). The processor andthe memory can be supplemented by, or incorporated in, special purposelogic.

It should be noted that the term “example” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

As utilized herein, the terms “substantially” and similar terms areintended to have a broad meaning in harmony with the common and acceptedusage by those of ordinary skill in the art to which the subject matterof this disclosure pertains. It should be understood by those of skillin the art who review this disclosure that these terms are intended toallow a description of certain features described and claimed withoutrestricting the scope of these features to the precise arrangementsand/or numerical ranges provided. Accordingly, these terms should beinterpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the inventions as recited inthe appended claims.

As used herein, the term “approximately” generally mean plus or minus10% of the stated value. For example, about 0.5 would include 0.45 and0.55, about 10 would include 9 to 11, about 1000 would include 900 to1100.

The term “coupled” and the like as used herein mean the joining of twomembers directly or indirectly to one another. Such joining may bestationary (e.g., permanent) or moveable (e.g., removable orreleasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

It is important to note that the construction and arrangement of thevarious exemplary embodiments are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements;values of parameters, mounting arrangements; use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein.Additionally, it should be understood that features from one embodimentdisclosed herein may be combined with features of other embodimentsdisclosed herein as one of ordinary skill in the art would understand.Other substitutions, modifications, changes, and omissions may also bemade in the design, operating conditions, and arrangement of the variousexemplary embodiments without departing from the scope of the presentembodiments.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyembodiments or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularembodiments. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

What is claimed is:
 1. An aftertreatment system configured to reduceconstituents of an exhaust gas produced by an engine, comprising: afirst filter; a second filter disposed downstream of the first filter; abypass conduit fluidly coupling an exhaust gas flow path downstream ofthe first filter and upstream of the second filter to an exhaust gasflow path downstream of the second filter; a valve operatively coupledto the bypass conduit, the valve moveable between a closed position inwhich the exhaust gas flows through the second filter, and an openposition in which at least a portion of the exhaust gas flows throughthe bypass conduit so as to bypass the second filter; and a controlleroperatively coupled to the valve, the controller configured to:determine whether a first filtration efficiency of the first filter isgreater than a first filtration efficiency threshold or less than orequal to the first filtration efficiency threshold; and control thevalve such that the valve is more closed when the first filtrationefficiency is less than or equal to the first filtration efficiencythreshold than when the first filtration efficiency is greater the firstfiltration efficiency threshold, such that a larger portion of theexhaust gas flows through the second filter when the first filtrationefficiency is less than the first filtration efficiency threshold, thecontrolling of the valve causing the exhaust gas expelled into theenvironment from the aftertreatment system to have a particulate mattercount which is lower than a predetermined threshold.
 2. Theaftertreatment system of claim 1, wherein the valve is initially in theclosed position in which substantially all of the exhaust gas flowsthrough the second filter, and wherein in response to the firstfiltration efficiency being equal to or greater than a first filtrationefficiency threshold, the controller moves the valve into the openposition such that more of the exhaust gas flows through the bypassconduit than the second filter.
 3. The aftertreatment system of claim 1,wherein the first filtration efficiency threshold corresponds to an ashload of approximately 0.1-10 g/L on the first filter for a mileage ofthe engine of less than 5,000 miles.
 4. The aftertreatment system ofclaim 1, wherein the controller is further configured to; determine afirst pressure drop across the first filter; and determine a flow rateof the exhaust gas, wherein the controller is configured to determinethe first filtration efficiency based on the first pressure drop and theflow rate of the exhaust gas.
 5. The aftertreatment system of claim 4,wherein the controller is further configured to: determine a secondpressure drop across the second filter; in response to the secondpressure drop being greater than a predetermined pressure dropthreshold, increase opening of the valve so as to allow at least aportion of the exhaust gas to bypass the second filter.
 6. Anaftertreatment system configured to reduce constituents of an exhaustgas produced by an engine, comprising: a first filter; a second filterdisposed downstream of the first filter; a bypass conduit fluidlycoupling an exhaust gas flow path downstream of the first filter andupstream of the second filter to an exhaust gas flow path downstream ofthe second filter; a valve operatively coupled to the bypass conduit,the valve moveable between a closed position in which the exhaust gasflows through the second filter, and an open position in which at leasta portion of the exhaust gas flows through the bypass conduit so as tobypass the second filter; and a controller operatively coupled to thevalve, the controller configured to: determine whether the engine isoperating in a high particulate matter operating condition or a lowparticulate matter operating condition; control the valve such that thevalve is more closed during the high particulate matter operatingcondition of the engine than during the low particulate matter operatingcondition of the engine, such that a larger portion of the exhaust gasflows through the second filter during the high particulate matteroperating condition of the engine than during the low particulate matteroperating condition of the engine, the controlling of the valve causingthe exhaust gas expelled into the environment from the aftertreatmentsystem to have a particulate matter count which is lower than apredetermined threshold, wherein the valve is positioned at an inlet ofthe bypass conduit, the valve comprising: a first ring defining aplurality of first openings, and a second ring defining a plurality ofsecond openings, the second ring abutting the first ring, wherein, inthe closed position, the plurality of first openings are misaligned withthe plurality of second openings such that the exhaust gas flows throughthe second filter, and wherein the second ring is configured to rotaterelative to the first ring to move the valve into the open position inwhich the plurality of first openings are aligned with the plurality ofsecond openings such that at least a portion of the exhaust gas flowsthrough the plurality of first and second openings into the bypassconduit around the second filter.
 7. The aftertreatment system of claim6, wherein the controller is configured to: in response to the engineoperating under the high particulate matter operating condition, causethe valve to be open a first predetermined amount such that the valve ismore closed than open so as to cause a larger portion of the exhaust gasto flow through the second filter than through the bypass conduit; andin response to the engine operating under the low particulate matteroperating condition, cause the valve to be open a second predeterminedamount such that the valve is more open than closed so as to cause alarger portion of the exhaust gas to flow through the bypass conduitthan through the second filter.
 8. The aftertreatment system of claim 6,wherein the second filter has a smaller pore size than the first filtersuch that the second filter has a higher filtration efficiency than thefirst filter.
 9. The aftertreatment system of claim 6, furthercomprising a selective catalytic reduction system positioned downstreamof the first filter and upstream of the second filter.
 10. Theaftertreatment system of claim 6, wherein the high particulate matteroperating condition corresponds to a larger amount of particulate matterbeing present in the exhaust gas produced by the engine relative to thelow particulate matter operating condition.
 11. The aftertreatmentsystem of claim 6, wherein the second filter has a smaller diameter thanthe first filter and the bypass conduit is positioned around the secondfilter.
 12. The aftertreatment system of claim 6, wherein the bypassconduit is defined through the second filter and the valve is disposedin the bypass conduit within the second filter.
 13. The aftertreatmentsystem of claim 6, wherein the controller is further configured to:determine a temperature of the exhaust gas; and in response to thetemperature of the exhaust gas being above a predetermined temperaturethreshold, close the valve so as to force hot exhaust gas to flowthrough the second filter for regenerating the second filter.
 14. Theaftertreatment system of claim 13, further comprising: an oxidationcatalyst disposed upstream of the first filter; and a hydrocarboninsertion assembly configured to insert hydrocarbons into the oxidationcatalyst, wherein the controller is further configured to instruct thehydrocarbon insertion assembly to insert hydrocarbons into the oxidationcatalyst for raising the temperature of the exhaust gas above thepredetermined temperature threshold.
 15. An aftertreatment system forreducing constituents of an exhaust gas produced by an engine,comprising: a first filter; a second filter disposed downstream of thefirst filter; and a controller operatively coupled to the first andsecond filters, the controller configured to: determine a firstfiltration efficiency of the first filter during operation of theaftertreatment system; and in response to the first filtrationefficiency being equal to or greater than a first filtration efficiencythreshold, generate a fault code instructing a user to remove the secondfilter from the aftertreatment system.
 16. The aftertreatment system ofclaim 15, further comprising a second filter pressure sensor operativelycoupled to the second filter, and wherein the controller is furtherconfigured to: interpret a pressure signal from second filter pressuresensor to determine a pressure drop across the second filter; and inresponse to the pressure drop being greater than a predeterminedpressure drop threshold, generate the fault code.
 17. The aftertreatmentsystem of claim 15, further comprising a first filter pressure sensoroperatively coupled to the first filter, and wherein the controller isfurther configured to: interpret a pressure signal from the first filterpressure sensor to determine a first pressure drop across the firstfilter; and determine a flow rate of the exhaust gas, wherein the firstfiltration efficiency is based on the first pressure drop and the flowrate.
 18. An aftertreatment system configured to reduce constituents ofan exhaust gas produced by an engine, comprising: a first filter; asecond filter disposed downstream of the first filter; a bypass conduitfluidly coupling at least one of an exhaust gas flow path upstream ofthe first filter to an exhaust gas flow path between the first filterand the second filter or an exhaust gas flow path between the firstfilter and the second filter to an exhaust gas flow path downstream ofthe second filter; a valve operatively coupled to the bypass conduit,the valve moveable between a closed position in which the exhaust gasflows through the second filter, and an open position in which at leasta portion of the exhaust gas flows through the bypass conduit so as tobypass the second filter; and a controller operatively coupled to thevalve, the controller configured to: determine whether the engine isoperating in a high particulate matter operating condition or a lowparticulate matter operating condition; control the valve such that thevalve is more closed during the high particulate matter operatingcondition of the engine than during the low particulate matter operatingcondition of the engine, such that a larger portion of the exhaust gasflows through the second filter during the high particulate matteroperating condition of the engine than during the low particulate matteroperating condition of the engine, the controlling of the valve causingthe exhaust gas expelled into the environment from the aftertreatmentsystem to have a particulate matter count which is lower than apredetermined threshold, wherein the valve is positioned at an inlet ofthe bypass conduit, the valve comprising: a first ring defining aplurality of first openings, and a second ring defining a plurality ofsecond openings, the second ring abutting the first ring, wherein, inthe closed position, the plurality of first openings are misaligned withthe plurality of second openings such that the exhaust gas flows throughthe second filter, and wherein the second ring is configured to rotaterelative to the first ring to move the valve into the open position inwhich the plurality of first openings are aligned with the plurality ofsecond openings such that at least a portion of the exhaust gas flowsthrough the plurality of first and second openings into the bypassconduit around the second filter.
 19. The aftertreatment system of claim18, wherein the first filter has a smaller pore size than the secondfilter such that the first filter has a higher filtration efficiencythan the second filter.